Ac power regulator with magnetic amplifier



; March 12, 1968 T. F. MAKA 3,373,347 j AC POWER REGULATOR WITH MAGNETIC AMPLIFIER Filed Jan. 21, 1965 A.C. INPUT TERMINALS D-C CONTROL M EA N S I 2 /600005 F' fiE/T'Z I BY ATTORNEYS United States Patent 3,373,347 AC POWER REGULATOR WITH MAGNETEC AMPLIFIER Theodore F. Maha, Winfield, lliL, assignor to Basic Products Qorporation, Milwaukee, Wis, 21 corporation of Wisconsin Filed Jan. 21, 1965, er. No. 426,820 4 Claims. (Cl. 323-89) ABSTRACT OF THE DHSQLOSURE A power modulator for regulating an A.C. voltage or current delivered to a load in which a main winding connected across the A.C. input comprises two series connected sections each mounted on spaced apart legs of a shell type core structure. A buck-boost auxiliary winding adapted to be connected in series with the load is wound on a central or intermediate leg having an air gap therein and so positioned as to receive magnetic flux in opposite directions from the spaced-apart legs. Separate D.C. control windings for each of the spaced-apart legs control the level of magnetic saturation or reluctance in the legs thereby to control the flux distribution within the core.

This invention relates to power modulators for use as line voltage regulators or constant current regulators.

In the prior art, devices for regulating voltage or current have been relatively bulky and expensive. One problem has been that the wave forms have tended to be unsatisfactory and so relatively large volumes of core material have been utilized and large numbers of turns were employed in the windings in an eiiort to maintain relatively low maximum fiux densities and thus to obtain satisfactory wave forms. However, this large amount of material and numerous turns have caused such prior devices to be bulky and to be expensive. Also, a problem has been that such prior devices have often not been as fast in their response as desired for continuous accurate control.

One of the objects of this invention is to provide a relatively inexpensive power modulator for providing a wide range of control.

Another of the objects of the invention is to provide a power modulator which is compact, fast in response, and produces a smooth regular wave form over the full range of operating voltages and over the full range of operating loads.

In one aspect of the invention, the core can be symmetrically constructed so as to include pairs of identical outer core legs positioned at opposite ends of the core. A single central core leg, which forms the fifth leg of the core structure, has approximately twice the cross sectional area of each of the individual outer legs, and this central core leg includes an air gap extending thereacross. An auxiliary winding is wound around this central leg and dual primary main winding sections are wound around the respective pairs of outer legs. Also, dual DC. control winding means are positioned on these respective pairs of outer legs for controlling their level of magnetic saturation or reluctance level to control the flux distribution within the core.

Further, it is an advantage of the illustrative embodimerit of the invention that it enables the amount of alternating flux and its relative sense of direction in passing through the central leg of the core to be controlled so that the single auxiliary winding on the central leg can serve the triple functions of acting as a bucking winding or acting as a boosting winding, or of being neutral as may be desired, depending upon the operating conditions.

The power modulator system as shown can be used in varlous circuits, one being shown herein which is especially useful for power or voltage output control. In this system, the dual primary main winding sections are connected in series across the source of power and the auxiliary winding is connected in series with the load in a position where it may provide a bucking effect, a boosting effect or substantially no effect, as the operating conditions may require. It is to be understood, however, that the invention can be applied to other circuits and arrangements. The term po'wer modulator means a device adapted for power, voltage and/ or current modulation.

In a further aspect of this invention, it is noted that although the dual primary main winding sections are called primary winding sections, they are not analogous to the two sections of a primary winding in an ordinary core-type transformer, because in this aspect of the invention there are large variations in the efiective mutual coupling and thus in the relative reactance of the respective primary main winding sections, depending upon the operating conditions, as will be explained in detail herein.

These and other objects, features and advantages of the present invention will be apparent from the following description and drawings which are merely exemplary of a presently preferred embodiment of the invention.

In the drawings:

FIGURE 1 illustrates one form of the five legged core in a power modulator system; and

FIGURE 2 is a perspective view of the core structure of FIGURE 1.

The invention first will be described in conjunction with a line voltage regulation system including a live legged core structure 16, as shown in FIGURES 1 and 2. The core structure 10 may have a pair of outer legs 11 and 12 of identical cross sectional area at one end of the core 10 and another identical pair of outer legs 14 and 15 of the same cross sectional area at the other end of the core, with a center leg 13 therebetween having an air gap 16 therein. All five of the legs 11-15 extend across in parallel relationship between a pair of spaced longitudinal back portions 17 and 18 of the core 10'. The center leg 13 has approximately twice the cross sectional area of any one of the outer legs 11, 12, 14 or 15, and similarly, the longitudinal back portions 17 and 18 have approximately twice the cross sectional area of any one of these outer legs.

First and second primary or main winding sections 20A and 20B are wound around the respective pairs of outer core legs 11 and 12, 1d and 15. An intermediate lead 19 serves to connect these two main winding sections MA and 2913 together in series between the input terminals 21A and 21B. It will be understood that the input terminals 21A and 21B are adapted to be connected to opposite sides of a suitable source of alternating current power, and thus the two main winding sections 20A and 20B are connected in series across the A.C. power source. Moreover, these winding sections 20A and 20B are wound and connected so as to be in series aiding relationship with respect to the magnetic flux induced in the core, as illustrated by the respective flux arrows and which, during one half cycle of the A.C. power source, all are directed effectively counterclockwise with respect to core 10. It will be understood that during the succeeding half cycle these flux arrows will all be reversed effectively so as to be in aiding relationship in the opposite sense.

In the form illustrated, there is an auxiliary winding 22 wound around the center leg 13. One terminal 23 of this auxiliary winding is connected to one of the input terminals 21B, and the other terminal 24 of this auxiliary winding is connected by a lead 25 to one of the output terminals 268. The other output terminal 26A is connected directly to the input terminal 21A by means of a lead 27. Thus, the auxiliary winding 22 is in series relationship between the input terminal 21B and the connection 25 extending to one side of the load 44, while the other side of the load is connected directly to the other input terminal 21A.

In order to control the flux distribution within the core 10, a first direct-current control winding 31 is wound in two halves around the pair of legs 11 and 12, passing through the winding window 33 which is located between these two legs. The two sections of this control winding 31 are connected in series with their winding sense being in opposition with respect to the A.C. flux linkage so as to cancel out any net A.C. voltage which would otherwise be induced in the control winding 31. Similarly, a second control winding 32 is wound in two halves around the pair of legs 14 and 15, passing through the winding window 36 between these two legs. The two sections of this control winding 32 are connected in series with their winding sense also being in opposition with respect to the A.C. flux linkage so as to cancel out the A.C. voltage induced therein. The ends of the control winding 31 are connected to the terminals 37 and 38 of a controllable source 40 of direct current, and the other control winding 32 is connected to the terminals 41 and 42 of this control means 41 To sense the voltage being supplied to the load 44 a pair of sensing leads 45 and 46 are connected from the control means 40 to the output terminals 26A and 26B.

The D.C. control means 40 may be any suitable source of direct current together with means to control independently the magnitude of the direct current supplied to the respective control windings from the pairs oi terminals 37 and 38, 41 and 42. Suitable D.C. control means 40 are known to those skilled in the art. For example, this D.C. control means 40 may include a reference voltage source such as provided by Zener diode circuits or voltageregulator neon tube circuits. Also, this D.C. control means 40 may include controllable rectifiers, either tube type or solid state type, such as Thyratron gas tube rectifiers or silicon controlled rectifiers, with the output from these rectifiers being filtered by smoothing filter circuits.

The operation of the saturable power regulator system as shown in FIGURE 1 is described hereinafter. When neither D.C. winding 31 or 32 is energized, then the alternating flux induced in core by the A.C. in the main winding sections 20A and B circulates in a closed path passing through the pairs of legs 11 and 12, 14 and and along the back sections 17 and 18, as indicated by the flux arrows and gb This flux mutually links with both winding sections 29A and B in a symmetrical pattern so that the reactance of both winding sections A and B are equal and none of this flux (p and from the two main winding sections passes through the center leg 13. Thus, the auxiliary winding 22 has no voltage induced therein. Consequently, the voltage supplied to the load 44 from the output terminals 26A and B is substantially equal to the applied voltage at the input terminals 21A and B. This is the operation condition when the applied A.C. voltage is equal to the desired voltage to be supplied to the load 44.

Assuming that the input voltage at the terminals 21A and B drops below the desired value, then direct current is caused to flow in the control winding 31, with substantially no current in winding 32. This induces D.C. magnetic flux to be present in the core legs 11 and 12 passing along a closed path in the core which encircles the winding window 33, as indicated by the control flux arrow The presence of this D.C. control flux in the core legs 11 and 12 raises the level of their magnetic saturation of reluctance level, and hence it raises their reluctance to the passage of the A.C. flux so as to reduce the magnitude of this flux. As a result, the reactance of the main winding section 20A is reduced relative to the other section 20B and so a larger proportion of the applied voltage appears across winding section 2013 than appears across winding section 20A, hence increasing the flux Moreover, the increase in reluctance of the legs 11 and 12 diverts the flux from the end of the core so as to cause this flux qb to pass through the center leg 13, as indicated by the arrow thus inducing a voltage in the auxiliary winding 22 which is in aiding or boosting relationship with respect to the applied voltage.

Consequently, the output voltage is maintained at the desired level in spite of the fact that the input voltage has dropped below its desired nominal value. If the input voltage should drop further, then the magnitude of the D.C. control current in the winding 31 is further increased as to produce a larger aiding voltage in the auxiliary winding 22 to maintain the desired output voltage.

Assuming that the input voltage at the terminals 21A and B rises above the desired value, then direct current is caused to flow in the control winding 32, with substantially no current in winding 31. This induces D.C. magnetic flux to be present in the core legs 14 and 15, passing along a closed path in the core which encircles the winding window 36, as indicated by the control flux arrow 11: This D.C. control flux raises the level of magnetic saturation in the core legs 14 and 15 and so it raises their reluctance to the passage of the A.C. flux (p thus reducing the magnitude of the flux In this condition, the reactance of the main winding section 20B is increased relative to the reactance of the other section 20A. Thus a larger proportion of the applied voltage appears across the win-ding section 26A, increasing the magnitude of the Also, the increase in reluctance of the legs 14 and 15, diverts the flux M1 SO as to pass through the center leg 13, as indicated by the arrow (p This flux qb induces a voltage in the auxiliary winding 22 which is in opposing bucking relationship with respect to the applied voltage.

As a result, the output voltage to the load is held at the desired level in spite of the fact that the input voltage has risen above the desired nominal value. Upon any further rise in the input voltage the magnitude of the D.C. current in the control winding 32 is further increased so as to produce a large bucking voltage in the auxiliary winding 22 to maintain the desired output voltage.

By way of example, a voltage regulator having a load rating of 5 kva. and a rated input voltage of volts was connected in a circuit similar to FIGURE 1. The length of the core was 10 /2 inches, the width 6 inches and the stack height 3 /2 inches, and the length of all five core legs was 2 inches, with the width of both back sections 17 and 18 also being 2 inches. The center leg 13 was 2 inches wide with a gap 16 of 0.020 of an inch, and each of the outer legs 11, 12, 14 and 15 was 1 inch wide. The windows 33 and 36 were 1 inch wide, and the two windows 47 and 48 adjacent to the center leg 13 were each 1% inches wide. The primary winding sections 20A and B each included only 58 turns and the auxiliary winding 22 only included 10 turns.

It should be apparent that various changes may be made in the details of the power regulator without de' parting from the scope of the invention as defined in the appended claims.

What is claimed is:

1. A power modulator for controlling power delivered from an A.C. source to a load comprising a core having a pair of parallel back portions with five core legs extending in spaced parallel relationship between said back portions, said five legs defining first and second pairs of outer legs and a center leg, said center leg having an air gap therein, a main winding having a pair of input terminals for connection to an A.C. source with first and second sections connected in series between said input terminals, said first and second sections of said main winding being wound around said first and second pairs of outer legs, first and second output terminals, an

auxiliary winding wound around said center leg and having one end connected to said first output terminal and the other end to one of said input terminals, said second output terminal being connected to the other of said input terminals, and first and second DC. control winding means for selectively controlling the magnetic reluctance level of said first and second pairs of outer legs.

2. A power modulator for controlling power delivered from an A.C. source to a load comprising a core having a pair of parallel back portions with five core legs extending in spaced parallel relationship between said back portions, said five legs defining firs-t and second pairs of outer legs and a center leg, said outer legs being of equal width and said center leg being approximately twice as wide as each of said outer legs and having a gap therein, a main winding having a pair of input terminals for connection to an A.C. source with first and second sections connected in series between said input terminals, said first and second sections of said main winding being wound around said first and second pairs of outer legs, first and second output terminals, an auxiliary winding wound around said center leg and having one end connected to said first output terminal and the other end to one of said input terminals, said second output terminal being connected to the other of said input terminals, and first and second DC. control Winding means for selectively controlling the magnetic reluctance level of said first and second pairs of outer legs.

3. A power modulator for controlling power delivered from an A.C. source to a load comprising a core structure having a pair of spaced back portions with five core legs extending in spaced parallel relationship between said back portions, said five legs including first and second pairs of outer legs and a center leg therebetween, said center leg having an air gap therein and each pair of outer legs having a window therebetween, a main winding having a pair of input terminals for connection to an A.C. source, said main Winding including first and second winding sections connected in series between said input terminals, said first and second winding sections being wound around said first and second pairs of outer legs in series aiding relationship with respect to A.C. magnetic flux mutually linking said winding sections and following a closed path travelling along one of the back sections of the core through the first pair of outer legs along the other back section and through the second pair of outer legs to return to the initial point, first and second output terminals, an auxiliary winding wound around said center leg and having one end connected to said first output terminal and the other end to one of said input terminals, said second output terminal being connected to the other of said input terminals, and first and second D.C. control windings, said first and second DC. control windings each being wound in two halves through the windows and around the individual outer legs of said first and second pairs for cancelling out any A.C. voltage induced therein.

4. A power modulator for controlling power delivered from an A.C. source to a load comprising core means having at least two spaced-apart legs and an intermediate shunt leg positioned to receive magnetic flux from said spaced-apart legs, said intermediate leg having an air gap therein, a main winding having a pair of input terminals for connection to an A.C. source, said main winding having first and second sections connected in series between said input terminals, each section being on ditterent spaced-apart legs of said core means, first and second output terminals, auxiliary winding means having at least a portion thereof wound around said intermediate leg thereby to be affected by the direction of flux through said air gap, means connecting one end of said auxiliary winding to said first output terminal and the other end to one of said input terminals, said second output terminal being connected .to the other of said input terminals, and means selectively controlling the inductance of said first and second sections of said main winding so as to control the direction of flux in said intermediate leg having an air gap whereby said auxiliary winding operates as either a boosting winding or a bucking winding.

References Cited UNITED STATES PATENTS 1,968,346 7/1934 Neiss 32356 X 1,997,657 4/1935 Schmutz 323-45 2,535,154 12/1950 Oestreicher 323--6O 2,665,406 1/1954 Carmichael 32345 2,804,583 8/1957 Genuit 323--56 X OTHER REFERENCES British printed application, 412,545, September 1932.

JOHN COUCH, Primary Examiner.

WARREN E. RAY, Examiner. 

